Rocks Tell the Story

Geology majors Emily Diener ’15 and Eric Stephens ’15 spent two weeks in Montana at Glacier National Park, collecting core samples from the bottom of two lakes in the Many Glacier Valley. The project is a continuation of previous studies in the park, also led by their mentor, Macalester geology professor Kelly MacGregor.

“With the growing pool of data from this chain of lakes,” says Diener (Duluth, Minn.), “we are able to study the climate, fire, and vegetation history of this glacial basin, and to use geologic markers like ashfalls from known volcanic eruptions to time stamp the sediment cores. We are also seeking to correlate and connect the cores within the chain of lakes to learn about how Grinnell Glacier has changed size over the last 20,000 years.”

This summer research experience was funded by the Keck Geology Consortium, which provides undergraduates with unique, high-quality field and research experiences. The students applied in the spring and received a stipend for two weeks of fieldwork and two weeks back in the lab at Macalester.

Stephens was born in Anchorage, Alaska, but has lived all over the world with his State Department parents. He declared a geology major in his sophomore year after his first class with MacGregor.

“My research focused on the Belt Supergroup, a series of 1.4 billion-year-old rocks that were thrust over younger Cretaceous sediments,” says Stephens. “I sampled a series of argillites, which are clay and mudstones, and stromatolites, which are the oldest fossilized life on Earth.

“My goal is to chemically tie sediments from lakes in the valley to certain elemental signatures in the surrounding rocks. We can then better understand if the lake sediment is being supplied by glacial processes, landsliding, or streams, and if the source of the sediment changes with climate.”